Variable Band-Elimination Filter With Grounded Switching Resonators
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Solution Overview
Problem
Existing variable-frequency band filters are large, costly, and complex due to the need for multiple filters and paths, with deteriorated filter characteristics from parasitic inductance components when diodes are used to change capacitance values.
Innovation Solution
A variable-frequency band-elimination filter with series resonance circuits defined by inductors and capacitors, a multistage T-shape matching circuit, and a switching element (such as an FET) connected directly to ground, allowing for frequency shifting without adding inductance components to capacitors, reducing the number of components and maintaining filter quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple filters with different characteristics are disposed in separate paths and switching is performed using switches, then frequency band switching is achieved, but the size of the transmission/receiving module increases and the system configuration becomes complicated
Solution Approach 1:
The patent combines multiple filter functions into a single integrated filter structure. Instead of having separate filters for different frequency bands, the invention uses one filter with adjustable resonance frequencies achieved through variable capacitors, thereby reducing the number of components and simplifying the overall system configuration while maintaining frequency band switching capability
Solution Approach 2:
The patent employs variable capacitors that can dynamically change their capacitance values to adjust the resonance frequencies of the filter. This dynamic adjustment allows a single filter to adapt to different frequency bands without requiring multiple fixed filters, thus reducing system complexity while preserving versatility
2Adaptability or versatility
If diodes and capacitors are used to change capacitance values in LC series resonance circuits, then frequency adjustment is achieved, but parasitic inductance components are added to the capacitors deteriorating filter characteristics
Solution Approach 1:
The patent extracts and removes the parasitic inductance problem from the system by avoiding the use of diodes in the capacitance adjustment mechanism. Instead of using diodes that introduce parasitic inductance, the invention uses alternative switching mechanisms that do not add harmful inductance components, thereby maintaining high filter characteristics quality while preserving frequency adjustability
Solution Approach 2:
The patent replaces expensive, high-quality capacitors that would be degraded by parasitic inductance with simpler capacitor implementations that can be switched without introducing parasitic effects. This substitution maintains the necessary frequency adjustment capability while avoiding the deterioration of filter characteristics
3Device complexity
If a single filter structure is used with variable capacitance, then device size and complexity are reduced, but maintaining excellent filter characteristics while shifting frequency becomes challenging
Solution Approach 1:
The patent uses variable capacitors that can dynamically adjust their capacitance values to change the resonance frequencies of the LC series resonance circuits. This dynamic capability allows a single simplified filter structure to maintain excellent filter characteristics across different frequency bands by adapting its electrical parameters in real-time
Solution Approach 2:
The patent changes the electrical parameters (capacitance values) of the filter components to achieve frequency shifting. By varying the capacitance in the LC series resonance circuits, the resonance frequencies are adjusted, allowing the single filter structure to maintain optimal performance characteristics across different operating frequencies
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution results in a smaller, lower-cost filter with improved filter characteristics, reduced power consumption, and the ability to shift frequency without degrading filter performance, using a single power source and simplified configuration.
Implementation Method 1
a first series resonance circuit defined by a capacitor C1 and a coil L1 which are on the side of an input terminal 1 and a second series resonance circuit defined by a capacitor C2 and a coil L2 which are on the side of an output terminal 2 are connected to each other via a coupling coil L4 as a parallel arm
Implementation Method 2
a variable frequency band filter is obtained by changing capacitance values using diodes
Data Source
AI summary
A series resonance circuit defined by a series circuit including an inductor and a capacitor and a series resonance circuit defined by a series circuit including an inductor and a capacitor are connected in shunt to a signal line. A diode is disposed between the grounding end of the series resonance circuit and the ground, and a diode is disposed between the grounding end of the series resonance circuit and the ground. The connection point between the grounding end of the series resonance circuit and the diode is connected to the ground via a frequency shifting inductor in a conductive state at high frequency, and the connection point between the grounding end of the series resonance circuit and the diode is connected to the ground via a frequency shifting inductor in a conductive state at high frequency. A matching circuit defined by a multistage T-shape LCL circuit is disposed between the series resonance circuits.